[Bug]: Avalonia for VSCode fails to recognize properties generated by CommunityToolkit.Mvvm

[DefaultCyberid]

Describe the bug

The Avalonia for VSCode extension is currently unable to resolve properties generated by CommunityToolkit.Mvvm (e.g., properties created via the [ObservableProperty] attribute).

While the project builds and runs successfully without any errors, the VS Code editor displays false-positive red squiggly lines (IntelliSense errors) indicating that these generated properties do not exist in the ViewModel.

To Reproduce

1. Create project with Avalonia.Mvvm template: dotnet new avalonia.mvvm -o MyAvaloniaApp
2. Change the Greeting variable in MainWindowViewModel.cs into a generated one:

   [ObservableProperty]
   public string _greeting = "Welcome to Avalonia!";

The {Text="{Binding Greeting}"} in MainWindow.axaml shows error: The property 'Greeting' does not exist on 'MyAvaloniaApp.ViewModels.MainWindowViewModel'.Avalonia(MC3073)

Product(s)

Avalonia for Code

Platform

macOS

License Tier

Community

Avalonia version

12.0.2

Tool/Control Version

12.2.0

Relevant log output

Additional context

No response

[mrlacey]

Hmmm. We fixed this issue previously.
Let me investigate...

[mrlacey]

@DefaultCyberid Can you provide more details about your environment, as I'm unable to reproduce the error you're seeing?

I'm testing with:

• VSCode version: 1.123.0
• Extension version: 12.2.1
• OS version: 25.3.0

In the project:

• Avalonia - v12.0.2 (and 12.0.4)
• CommunityToolkit.Mvvm - v 8.4.1

I verified the errors are correctly shown by changing the binding to something that doesn't exist and that did highlight the error.

If you look in the OUTPUT view and select "Avalonia Client" are any errors shown?

[DefaultCyberid]

VSCode 1.123.0
Extension 12.2.1 (updated 30 minutes ago)
macOS 15.7.7
Avalonia 12.0.2
AvaloniaUI.DiagnosticsSupport 2.2.1
CommunityToolkit.Mvvm 8.4.1

Nothing shown in "Avalonia Client" output, even if I restart the extension host.

Yeah it should have been fixed in 12.1.0, but I still can't get rid of it. The previous issue is [#57].

[mrlacey]

Some things to try:

1. Try setting the Log Level to Trace and then try rebuilding the project. There should be something in the output view, that' you're seeing nothing there is surprising.

2. Can you build and use source-generated code in non-Avalonia? (If not, this would suggest something beyond the extension.)
3. Can you try an older version of the CommunityToolkit library? or the suggestion here
4. Does a new Avalonia app that doesn't use the source generators build and run ok?

[DefaultCyberid]

After setting the log level to trace (up from error), I noticed the following warning, others are [info]s:

[warning] [EXT - WARN] No previewer target or active previewer process; cannot update preview.

I had closed the previewer beforehand, so I believe this is expected behavior and unrelated to the main issue.

I attempted to downgrade the CommunityToolkit.Mvvm package to version 8.0.0 and performed a clean rebuild and VSCode restart, the MC3073 error disappeared.

All my Avalonia projects compiles and runs perfectly without any warning or error, the only problem is the MC3073 error appears in the .axaml editor while the Avalonia for VSCode extension is active.

[the-pawn-2017]

Same error, I using windows 11/ .net sdk 8.0 、Avalonia 12.0.2 、CommunityToolkit 8.4.1。